Periodically, locomotives require inspection or repair. In addition, unmanned locomotives sometimes require boarding by personnel. Injury may be caused if a locomotive is moved while it is being inspected or repaired. Injury may also be caused if an unmanned locomotive begins moving while being boarded by personnel. In response to these safety concerns, railway companies have implemented blue flag safety procedures in which personnel working on a locomotive are required to place a physical blue flag on the locomotive. When such a flag is placed on the locomotive, no one is permitted to move the locomotive.
U.S. Pat. No. 5,816,541 issued Oct. 6, 1998 (the '541 patent) discloses a method of preventing movement of a locomotive while personnel are working on the locomotive. The method includes placing the brakes of the locomotive under the control of a card reading control box, and providing personnel employed to work on the locomotive with identification cards readable by the box. Each worker inserts his or her card in the box before working on the locomotive. The control box reads the cards and in response thereto maintains the brakes of the locomotive at full service until the personnel have left the locomotive and the control box is cleared. The application of this system has drawbacks. A better system is needed.